Sianipar, Ruth Sahanaya, Desi Sijabat, and Bernard Simanjuntak. “The Effect of Problem-Based Learning (PBL) on the Critical Thinking Skills of Fourth Grade Students”. Jurnal Ilmu Sosial dan Humaniora 4, no. 1 (January 31, 2026): 359–368. Accessed April 18, 2026. https://putrapublisher.org/ojs/index.php/isihumor/article/view/1495.